Cyathea ascendens is a species of tree fern native to northeastern New Guinea, where it grows in rain forest at an altitude of 800–1000 m. The erect trunk is slim and 1–2 m tall. Fronds are bi- or tripinnate and may be over 1 m in length. They form a distinctive open crown. The stipe is covered in glossy scales with pale, fragile adges. Sori occur near the midvein of fertile pinnules and lack indusia. The specific epithet ascendens implies that the species is a good climber, although there is no evidence of a true climbing habit.